It offers you visual protection against enemy intelligence, so you can safely have more than six men on the battlefield without getting mauled by artillery, air raids or by other enemy support. This requires you to "hide" troops under the cam net such that no more than six units are visible at any one time.
Of course, these are very fragile, and even the smallest explosion can destroy them. Therefore, it is advisable to have an engineer place some sandbags in front of them to absorb fragmentation. Try to save a handy 5 TP to replace if needed.
An enemy 1st. SS Leibstandarte can render these ineffective for 10 seconds, but they are not permanently damaged. However, within those 10 seconds, enemy support might be used on your position, so make sure you prioritise him quick.
Here's an image made by British:
The soldier is covered if the spot where you click to move him is within this area.
Cam Nets were rarely used in WW2 battlefield as they were not useful or practical in hiding troops. They were more common in military bases and in forest positions to hide them from airforce. Infantry used camouflage uniforms or other clothing and vehicles were painted. Ships were painted to confuse U-boat crews so they couldn't see how many ships they had spotted or to what direction they were heading. Modern day camouflage can, if done by experts, make a soldier fully disappear in their current surrounding environment depending on the uniform patterns and colours they are wearing.